A conventional femto base station is a small cellular base station, typically designed for use in residential, small business, or other environments in which the served coverage area is relatively small. Conventional femto base stations are usually installed indoors (e.g., in a home or office), and connected to a wireless service provider's core network via cable, a digital subscriber line (DSL), an on-premise fiber optic link, a similar Internet Protocol (IP) or other packet-based backhaul network. Conventional femto base stations provide improvements to both coverage and capacity of wireless networks. Femto base stations typically support about 2 to 5 mobile phones.
FIG. 1 illustrates a conventional femto cell or coverage area 110 served by a conventional femto base station 150. The femto base station 150 is connected to an Internet Protocol (IP) network 120, and incorporates the functionality of a typical base station in serving mobile stations 102-10M. This connection to the IP network 120 is used to integrate the femto base station 150 with the wireless operator's core network (not shown).
In order to implement and control usage of femto base stations, service providers must have reasonably accurate and reliable information regarding the location of femto base stations (e.g., residential or commercial) at the time of installation. This location information is necessary to determine, for example, the frequency band to which the femto base station should be tuned. As is well-known, frequency bands are dictated by service provider radio transmission licenses, which are dependent on geographic location. In addition, a femto base station must be tuned to the proper frequency band to comply with mandated government emergency response regulations concerning location (e.g., E911).
Cost constraints imposed by the femto cell market further require that conventional femto base stations be user deployable. As a result, femto base stations must employ a highly-automated process to put the femto base station in operation, which is only minimally augmented by the user. This highly automated process must provide the wireless network operator with the required location information for the femto base station, while also allowing the consumer the flexibility to place the femto base station at the location of their choice. Finally, the highly automated procedure must be robust in that once the femto base station is installed and its location is reported to the network, re-locating the femto base station does not go undetected and unreported.
Conventionally, a reliable source of accurate location information is the well-known global positioning system (GPS). A femto base station having a well-known GPS receiver is capable of automatically determining its location worldwide provided that the GPS receiver is able to successfully detect and decode GPS timing/tracking signals from a minimum number of satellites (e.g., normally greater than or equal to 4). However, a major obstacle to using GPS systems to determine and track the location of a femto base station is presented when the femto base station is located indoors because satellite signal penetration indoors is highly unreliable.
To overcome the building signal penetration problem, the GPS receiver in a conventional femto base station is commonly provided with an external antenna. The external antenna is placed at a location having sufficient signal transparency to the outside (e.g., typically attached to a window) such that the GPS receiver is able to successfully detect and decode GPS signals. But, this solution has its drawbacks. For example, in most cases the additional cost of the external antenna and cable are comparable to (if not the same as) the cost of the GPS receiver itself. In addition, this solution further burdens the user because the external antenna must be installed (usually permanently or semi permanently) on a window. Extra cables must also be routed around the residence or business in the event that Internet access is not located close to a window.